Preparation of isopropyl amines



Patented Apr. 18, 1950 UNITED STATES ATENT OFFICE PREPARATION OF ISOPROPYL AMINES No Drawing. Application April 15, 1947, Serial No. 741,697

This invention relates to the manufacture of isopropyl amines, and is directed more particularly to processes for the preparation of amine mixtures containing diisopropyl amine and predominating quantities of monoisopropyl amine.

Although it is known that amines may be made by reaction of ammonia with alkyl halides, the reaction of ammonia with alkyl sulfates to form amines has not been investigated to any great extent. The prior art suggests the preparation of methyl amine from dimethyl sulfate and am monia, but shows low yields which are manifestly attributable to the reaction of only one of the alkyl groups of the dialkyl sulfate with ammonia. Yields of this nature are too low to warrant economical commercial development.

This invention aims to provide processes which result in good yields of isopropyl amines from isopropyl sulfate starting materials. Another object of the present improvements is to afford processes by the practice of which it is possible to effect conversion of substantially both alkyl groups of diisopropyl sulfate to isopropyl amines. A further object is provision of processes for obtaining both mono and diisopropyl amines from readily available isopropyl sulfate materials.

In accordance with the invention I have found that if ammonia is reacted with a substantially anhydrous isopropyl sulfate under certain herein described temperatures, pressures and other conditions, good yields of isopropyl amines may be obtained. Further, I find that if ammonia is reacted with diisopropyl sulfate under these certain temperature, pressure and other conditions, substantially both alkyl groups of the diisopropyl sulfate are converted to isopropyl amines, this latter'observation being the apparent basis for obtaining isopropyl amine yields substantially in excess of those indicated as theoretically possible by the prior art.

Briefly, the process of the invention comprises effecting reaction of suitably chosen proportions of an isopropyl sulfate and ammonia by subjecting these materials to the action of elevated temperatures and pressures in an autoclave designed to accommodate the herein indicated temperatures and pressures of reaction.

The isopropyl sulfate starting materials used in accordance with the practice of the invention comprise diisopropyl sulfate, (C3H7)2SO4, isopropyl hydrogen sulfate or monoisopropyl sulfate, C3H7'HSO4, or mixtures thereof. Substantially pure diisopropyl sulfate may be utilized, or a starting material containing diisopropyl sulfate and preferably a minor proportion of monoiso- 13 Claims. (01. 260-585) I propyl sulfate may be employed. A readily obtainable and preferred sulfate starting material is diisopropyl sulfate liquor formed by gassing sulfuric acid with propylene.

A diisopropyl sulfate liquor may be prepared by gassing -l00% strength sulfuric acid with sufilcientpropylene to react with substantially all the acid to thereby form predominantly isopropyl sulfate. For example, gassing of the sulfuric acid with propylene is preferably effected at temperatures in the range of zero to minus 10 (3., and when utilizing 95-100% strength sulfuric acid about 2 mols of propylene are needed for each mol of H2504. The reaction probably proceeds as follows:

Use of an insufiicient quantity of propylene results in formation of some monoisopropyl sulfate, and although in accordance with the present invention it appears certain that the one alkyl group of this material reacts with ammonia to form the sought-for isopropyl amines, the overall amine yield will be higher if all of the ester is in the form of diisopropyl sulfate. Hence, in the gassing of the sulfuric acid it is preferred to employ such a sufficient excess of propylene that the monoisopropyl sulfate content of the diisopropyl sulfate liquor is minimized. The expression diisopropyl sulfate liquor as utilized in the appended claims is intended to designate a liquor which is or is comparable with the pro.- pylene-sulfuric acid reaction liquor described above and which may contain appreciable amounts of monoisopropyl sulfate and smaller amounts of free sulfuric acid and other impurities or inerts such as propylene polymers, isopropyl alcohol, diisopropyl ether and propane.

It is to be noted that the liquor made by propylene gassing of strong sulfuric acid is not a liquor which is merely free propylene absorbed in sulfuric acid as an absorption medium. Such liquor contains essentially diisopropyl sulfate and variable small amounts of isopropyl hydrogen sulfate and possibly free unreacted sulfuric acid. Thus, subsequent reaction of this liquor with ammonia is not a reaction between an olefin and ammonia, but rather between an ester and ammonia.

.If in=place of the above described diisopropyl sulfate liquor it is desired to use in the practice of-the invention substantially pure diisopropyl sulfate, the latter may be prepared as follows.

the ammonia distilled of! may be absorbed in an acid solution-such as hydrochloric acid, or collected in a trap suitably packed with dry ice'and maintained at a temperature of about .60 to were collected in condensers cooled with ice water. 8.5 parts of isopropyl amine and 1.1 parts of a liquid having a boiling range of 75-85 C. and taken as diisopropyl amine were recovered.

70 C. to effect condensation of the amines. If A yield of 72.0 mol per cent conversion to monothe volatilized amines are absorbed in the acid isopropyl amine and 11.4 mol per cent conversion solution, thereafter the solution may be evapoto'diisopropyl amine based on propylene, reprerated to dryness, and the solid amine and 'amsenting a total conversion of propylene to amine monium salts obtained as residue may be exof 83.4%, was thus obtained as summarized in tracted with a solvent such as anhydrous n-prorun No. 1 of the appended table. The monoisopanol to separate the amine from the ammonium pro-pyl amine and the vdiisopropyl amine were salts. The extract containing only the amine identified by their boiling points of about 34 C. salts may then be evaporated to dryness, leaving and 84 C. respectively. However, these amines the solid amine salts as residue which may then may be further identified by refractive index or be analyzed for carbon to determine the converby melting point of the purified hydrochloride sion of propylene to amines. The combined derivatives.

Priduft tYiefldC lisediosno Ogle oneno a---:4e- Anylatmg Agent M018 Mols NHa action Liquor;Recovered Time Temper CSHB per mol Amine Run No. H ature, Pressure, lbs. gauge Per M01 propylene "0. H so inreaction H1804 2 4 liquor Primary, Secondary, Agent Type Used, Mol per 01 per Total Per Cent cent cent C3H7NH2 (CzHfizNH 4 200 Autogenous 1000 lbs. CaHuHzSO4 Reac- 100 1.77 3.9 72.0 11.4 83.4

tion Liquor 4 250 Autogenous 1200 lbs. (1 100 1. 77 3.9 53.0 13.6 66.6 4 200 Autogenous 1700 lbs. 100 1.86 12.8 52.0 3.8 55.8 1 200 Autogenous 1200 lbs- 100.75 1.87 6.3 39.9 20.6 60.6

amine salts may be mixed with an alkali e. g. sodium hydroxide, and the resulting mass may be distilled at atmospheric pressure in a suitable column, e. g. one having about 15 theoretical plates and a reflux ratio of about 1 to separate the various amines, which are collected in a cooled receiver at about 0 C., the principal amine obtained, monoisopropyl amine, distilling over at about 32-34 C. with the diisopropyl amine'coming over at about 84 C.

If the amines evolved by the first mentioned distillation were collected in an ice trap, such amines may be separated by fractional distillation at atmospheric pressure without undergoing the additional treatment noted above.

Following is an example of practice of the invention. A propylene-sulfuric acid reaction liquor was made by propylene gasing of 100% sulfuric acid in proportions of about 1.77 mols of propylene per mol of 100% H2804. About 19.6 parts (by weight) of this propylene-sulfuric acid reaction liquor were placed in a chrome-vanadium steel autoclave. Approximately 3.9 mols of anhydrous ammonia per mol of propylene in the propylene-sulfuric acid reaction liquor were introduced into the autoclave, and the contents were brought to a temperature of about 200 C. by heating the autoclave in an oil bath. The reaction proceeded under the developed autogenous pressure which was about 1000 lbs. gauge. At the end of about 4 hours, heating was discontinued, the reaction mixture was cooled to about minus 70 C., the autoclave opened and about 80 parts of Water were slowly added with swirling to the mixture at this temperature to dissolve the amines and the salts. The diluted mass was warmed to about 0 C. The resulting aqueous solution was poured from the autoclave, neutralized by the addition of approximately 100 parts of a solution of sodium hydroxide, and distilled at atmospheric pressure using a small column. Ammonia was first removed following which isopropyl amine distilled over at about 34 C. and diisopropyl amine at about 84 C. The amines Runs 2, 3 and 4 were carried out in approximately the same manner as run 1. A propylenesulfuric acid reaction liquor was prepared as in run 1, placed in an autoclave, and ammonia introduced to initiate reaction which proceeded at autogenous pressure. The amines formed in runs 2 and 3 were recovered by the same procedure as for run 1. In run 4 the amines were recovered by absorption in hydrochlori acid as previously described.

It is noted that in runs 3 and 4 the yields were 55.8 and 60.5 total mol per cent of amines respectively as compared to 83.4 obtained in run 1 at about the same reactiontemperature, i. e. 200 C. While taking into account any effect on yields as a result of the different operating pressures employed in runs 1, 3 and 4, it appears that the use of such large quantities of ammonia as 12.8 and 6.3 mols per mol of propylene in the absorption liquor in runs 3 and 4 respectively indicate no particular advantage over the use of a smaller amount of ammonia on the order of about 4 mols per mol of propylene in the absorption liquor noted in run 1. However, the short reaction time of 1 hour for run 4 indicates the efiectiveness of my process even for short reaction periods.

I claim:

1. The process comprising reacting, under substantially anhydrous conditions, ammonia and an isopropyl sulfate at temperature not less than C. and at pressure not less than 750 lbs. gauge.

2. The process comprising reacting, under substantially anhydrous conditions, ammonia and an isopropyl sulfate at temperature in the range of 100-300 C. and at pressure in the range of 750-2500 lbs. gauge.

3. The process comprising reacting, under substantially anhydrous conditions, ammonia and diisopropyl sulfate at temperature not less than 100 C. and at pressure not less than 750 lbs.

gauge.

4. The process comprising reacting, under submacaw? fl sstan'tially anhydrous conditions, ammonia andea zdiisopropylrsulfate. liqu'orwat ten perature nota-less than 100 C. and 'ats-pressure not: less than 750 ,lbssg-auge.

P5. :The processcomprisingrreacting,under sub- ;stantially anhydrous conditions, ammonia and a diisopropyl sulfate liquorr' at temperaturein: the r :range of 100-300 C: and. at pressure in the range :of 750+2500=' 1bs. gauge, and recovering isopropyl -amine ifrom 'the; reactionaproducts.

The;process'-comprising 'reacting' anhydrous fammonia-xiand an -.anhydrous diisopropylsulf-ate liquor: atz-temperature not 165831311341), 100'f-,C.- and Lat :pressured'not less2than 750 lbs.'-;ga'uge.

stantially anhydrous conditions, ammonia- -nand an isopropyl sulfate at temperature not less than "1-00-C.--and--at autogenouspressure.

"1 23. flThei rocess-of zproducing isopropyl amine Which-comprises reacting, under substantially anhydrous conditions, ammonia and alpropylenesulfuric-acid reaction liquor atxa tempe'ratu-rein the range-of 100'-300=7C. and'at autogenous pres- "sure, andirecoveringthe isopropyl amine formed from the reaction products.

9. Theprocess of producing isopropyl amine Which I comprises reacting, under substantially, anhydrous conditions, ammonia andra diisopropyl isulfateliquor ;ati-a temperature-inYthe range of ISO- 250 C. and at autogenous pressure, and recovering the pyl amine formed from" the reaction products.

: *The process 6f"producing' -isopropy1 amine "Which-comprises reacting anhydrous ammonia with a -propy1ene sul'furicacid reaction liquor, "formed by treating 95-'100% sulfuriclacid with *suffi'cient propylene to reactwith substantiallyall or said 'acid "toform predominantly dii'sopropyl "sul fatep'ata temperature in "the range of 150- 250 C. and at'auto'genou's pressurefandre'coveb *ing the isop'ropyl amine formed from the reaction products.

' '11. "The process of "producing isop'ropyl amine "Whichpomprises reacting anhydrous ammonia with a propylene sulfuric acid-reaction liquor,

formed bytreating 95-1U0%' sulfuric a'cid with '8 v,p ropylen'ewinaa-rratiowof 2 mole-of propylene gper .qnol of H2804 wherebydiisopropyl sulfateds :p'res domina'ntly;;produced,aat, a temperature in :the range of 150-250 v and'at pressure in therange 16f 7507-72500 -lbs sgauger from -2 to 5 :mols ":ofnanhydrous --ammonia being employed '3 per mols-of propy1ene in said reaction liquor, and recovering the isoprqpyl'iamine formed from the-reaction product. 7,

z-'12.;The:-pro'cess of producing isopr-opykamines t :which' #COmpliSBS introducing lsuflicient propylene *in'to -100 %:-sulfuric acidto:reactwithsubstanitially all ofsaid acid-to form a propylene-sulfuric :racid reaction liquoncontaining;predominantlyEdiisoprqpylisulfatenreacting to 5 mols of= anhy idrou'srammoma per-mol of: propylene :in 'said::-re-

action liquor with said liquor at a temperature in the range of 150-250 C. and at autogenous pressure, and recovering visopropyl amine and adiisopropyl amine from the reaction products.

18. The process of producing isopropyl amines whichcomprises-introducing about 2&mols-of=propylene into each mol of approximately sulfuri'c acid to react with substantially all of said acid to form a reaction liquor containing predom inantly diisopropyl sulfate, reacting 3 to 5 mols of anhydrous ammonia per-mol of ,propylene in said frea'ction liquor with said liquor. at a temperaturesn the; range of i 200-250" C.. and "at autog enous pressure 'for "a period up to about 5 hours, a-ndrecovering -isopropyl amine and-diisoiwilson Dec. '5, 1944 

1. THE PROCESS COMPRISING REACTING, UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS, AMMONIA AND AN ISOPROPYL SULFATE AT TEMPERATURE NOT LESS THAN 100*C. AND AT PRESSURE NOT LESS THAN 750 LBS. GAUGE. 